Chapter 18 G.3 Impact of Humans on Ecosystems
The Simpson Diversity Index The diversity index gives two important measurements: richness: the number of species in an ecosystem evenness: the abundance of a species The Diversity Index is measured by the following formula: n = number of individuals of each species N = number of organisms in the ecosystem Reasons for and against Conservation of Biodiversity Four main reasons to argue the conservation of any ecosystem; here, rainforests are used as an example. Economic: rainforest soils being converted to farmland has no yield, and ofers no benefit to farmers. Furthermore, ecotourism is a source of money which is removed through the destruction of these ventures. However, clearning rainforests does provide more ground for construction. Ecological: rainforests can affect their surrounding ecosystems; furthermore, diversity protects from alien species invasion. With this removal, they are vulnerable to destruction by other species. However, they do harbour insects which are carriers of deadly diseases. Ethical: Do we have the right to destory rainforests? Can we attack the earth so? These are ethical questions which ask if this generation of humanity can deprive the future ones of these ecosystems. Furthermore, can we decide which species live or die? Those in disagreement with conservation say yes - humans are a species, and can affect all they need to. We are on this earth, and must use it according to our necesities. Aesthetic: Rainforests are beautiful, proponents claim. Of course, those with conflicting taste say otherwise. This ties into ethics as well - can we deprive humanity and the earth of something people consider beautiful? On Alien Species - Their Introduction and Impact Non-native species can disrupt and out-compete native ones. This reduces biodiversity, and can have a significant impact ont he ecosystem. Kudzu, an example Kudzu was introduced from Japan to the United States as an ornamental plant. Since then, it has taken over incredibly fast , dubbed 'the plant that ate the south.' It grows both horizontally and vertically, literally strangling plant life in its path. Up to $500 million has been lost to Kudzu damages. Classifying Impact ' ''Interspecific competition: A species outcompetes another, native one e.g. the red squirrel in the UK was outcompeted by the American grey squirrel. Predation: One species eats another species, e.g. the sea lampreys in the great lays can eat trout, and decimated their and the whitefish's populations quickly. Species extinction: By either of the methods above, or others, a species can outcompete a native one completely, leading to its annihilation and thus extinction (e.g. the Carolina Parakeet). '''On Biological Control of Invasive Species The idea of Biological Control is fairly simple - use a natural predator that does not affect other parts of the ecosystem (despite of rigorous testing, this is a difficult goal to achieve) to control these species. Examples: Prickly Pears Prickly pears are under biological control - that is, once scientists in Australia realized its devastating effects, a moth (cactoblastic cactorum) that feeds only on the prickly pear was introduced. THis controls the pear, and results in a balance between the two populations. Red Fire Ants An imported pest in the United States, they are common in southern states already and spreading to the north. They compete with normal ants, and would soon have become the dominant species. However, scienists are experimenting with the phorid fly, a fly which hovers over a mound of red ants and works on laying eggs to decaptiate them. Effects of UV Radiation *Skin cancer (lethal, non-lethal) *DNA mutation *Sunburn *Cataracts *Reduced productivity (e.g. plant cells dying) CFCs and the Ozone Layer Ozone is a protective layer on the planet, which absorbs UV radiation (about 20km thick). It occurs were O2 breaks down to rebond as O3, about 15-35km above the Earth's surface. It is, however, thinning because of cluorofluorocarbons (CFCs), such as: *refrigerator coolants; *propellants for aerosols; *material used to make foam packaging These break down to release chloride ions, which reacte with ozone molecules to form CIO, which can produce more oxygen gas an choride ions, etc. forming a chain to destroy yozone.